I have a legacy in America, but I'm waiting for my immigrant visa application. My husband died unexpectedly in America, and I can still.

Yes, I can automatically transfer to I-360, widow visa. The following is the explanation of official website, the Immigration Bureau, but I don't know if I need a guarantee from my relatives. I've seen cases of asking for guarantee before, but I don't know if it has changed now.

Widows (widowers) whose immigration applications are pending or approved.

If you are married to an American citizen and submitted the I- 130 Application for Foreign Relatives for you before his or her death, you don't need to submit any documents. Form I- 130 will be automatically converted into form I-360, which can be applied for amerasians, widows or special immigrants. If you have children (unmarried and under 2 1), they may be included in the I-360 form, regardless of whether your deceased spouse submitted an application for them.

To qualify, you must not have divorced or legally separated from an American citizen at the time of your death. If you remarry, your qualification as a widow immigrant will be terminated.